Você pode usar a classificação sobre a partição assim:
select * from
(select locid, value1, value1date,
rank() over (partition by locid order by value1date desc) as rank
from table1) t
where t.rank=1
Consulte SqlFiddle
select * from
(select locid, value1, value1date,
rank() over (partition by locid order by value1date desc) as rank
from table1) t
where t.rank=1
